Vascular atherosclerotic lesions that create arterial luminal narrowing are typically treated in angioplasty procedures via catheters provided with a balloon. The catheter is advanced, typically following a guidewire, to an opening within the atherosclerotic lesion of the narrowed artery. Once the balloon has been arranged at the artery narrowing, it may be inflated and deflated, sometimes repeatedly. The inflation, with successive deflation, of the balloon within the artery can reduce the extent of the arterial luminal narrowing, and restore a suitable blood flow.
In many cases, patients develop a new narrowing of the vessel lumen at the intervention point within a few months. Such narrowing, or restenosis, is due to a cell hyperproliferation process, particularly of the vascular smooth muscle cells, probably due to the dilating action caused by the balloon.
Balloons can be coated with a drug having anti-proliferative action to prevent or retard restenosis. Among the drugs usually employed to such aim, paclitaxel (taxol) has proved to be particularly efficient.
However, the majority of solid phase paclitaxel is rapidly cleared from the target site to the distal vasculature, usually occurring within days of treatment. This clearance is thought to be associated with the mechanical interaction of active blood flow and the resulting wall shear stress with the solid phase drug adherent to the vessel wall.
Consequently, the drug dose coated onto the balloon is empirically determined to take this loss into account. However, more efficient retention of drug on the vessel wall at the site of treatment would be beneficial to facilitate lower doses of drug on the balloon and lower drug exposure to distal tissues.